This invention relates to a method and apparatus for cleaning a petroleum emulsion.
A major environmental problem for many oil companies is the cleaning of petroleum emulsions containing large quantities of water and dirt. In general, the production of crude oil yields petroleum emulsions containing water and dirt (particulate material). This is particularly true when using steam flooding methods in the production of petroleum. Production tanks and pits containing petroleum with a high B.S. & W. (basic sediments and water) content cannot be pumped in a pipeline until the dirt and water have been removed. Refineries also accumulate dirty emulsions of water and oil in their sewer systems and A.P.I. separators. Oil separation by air floatation, pond skimming, etc. yields a mixture of oil, water and dirt. Storage tanks permit the water and dirt to settle to the bottom of the tanks, and the tanks must be cleaned periodically. In every case, petroleum can be recovered if the dirt and water can be separated from the emulsion. The recovered petroleum can then be recycled to a refinery for processing.
Attempts have been made to separate dirt and water from such emulsions in an efficient manner. Examples of the art relating to apParatuses and methods for separating water and dirt from petroleum emulsions are found in Canadian Patent No. 1,201,403, which issued to L. Bland on Mar. 4, 1986 and U.S. Pat. No. 4,334,605, which issued to F. A. Hitt on June 15, 1982. While these patents disclose methods and apParatus designed to separate water and dirt from oil, there still exists a need for an efficient and economical process and apparatus for cleaning an emulsion whereby the water recovered therefrom is sufficiently clean to meet existing standards for disposal or reuse, and the dirt is sufficiently clean to permit the disposal of the dirt as landfill.
The object of the present invention is to meet the above need by providing a relatively simple process and apparatus for separating water and/or dirt from a petroleum emulsion, so that the petroleum is acceptable for use in a refinery, and the separated water and dirt are clean enough to meet or exceed environmental safety standards.
According to one aspect, the present invention relates to a method of removing dirt and water from a petroleum emulsion comprising the steps of:
(a) screening the emulsion to remove large, non-pumpable impurities;
(b) heating the emulsion to decrease the viscosity thereof;
(c) separating dirt from the emulsion;
(d) mixing the dirt with a fuel to dilute residual petroleum on the dirt with fuel thereby producing a combustible mixture;
(e) burning the combustible mixture and using the heat produced therefrom to evaporate water from the emulsion to yield a clean petroleum of low water and dirt content; and
(f) using residual heat in the clean oil to heat the emulsion in step (b).
According to another aspect, the invention relates to an apparatus for removing dirt and water from a petroleum emulsion comprising:
(a) screen means for removing large, non-pumpable, impurities from the emulsion;
(b) heater means for heating the emulsion to reduce the viscosity thereof;
(c) separator means for removing dirt from the emulsion;
(d) mixing means for mixing the dirt with fuel to product a combustible mixture of residual petroleum from the dirt and fuel;
(e) burner means for burning the combustible mixture;
(f) evaporator means for receiving heat from said burner means to evaporate water from the emulsion to yield a clean petroleum of low water and dirt content; and
(g) petroleum discharge means for discharging clean, warm petroleum from said evaporator means through said heater means for heating the emulsion by heat exchange.
The process and apparatus are intended for use with petroleum emulsions ranging from heavy crude oils to light crude oils, and with refinery products or wastes containing water and/or dirt.